How to make a docked control resizeable by the user?

I have a Form with a control (a SplitContainer) docked on the right side. The width of the control can be changed in the editor, but not at runtime. What do I have to do to make the docked control resizable by the user?

The rest of the f开发者_StackOverfloworm should be a MdiContainer. So as far as I see, other containers are not usable, because they can not contain MDI children.

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Try docking a Spliter control next to your control.